always run the extensions/core funcrefs last.

this ensures the user always has priority in customizations.
test funcref pipeline.
redefine mode as a raw part.
basic support for hiding based on win size per part (#200).
lazy load variables until needed (#204).

this allows users to define section variables in their vimrc.
test removal of funcrefs
make it possible to declare sections in the vimrc (#204).
test for window switching and active/inactive splits.
improve loading performance
document configuring with parts and sections.
move part declarations back into init.
Merge branch 'master' into dev

Conflicts:
	doc/airline.txt
test for warning sections enabled in active splits.
much smarter handling of separators (#204).
update documentation about section functions.
add screenshot for fine tuned configuration. resolves #204.
document minwidth. resolves #200.
Merge branch 'master' into dev